1. Field of the Invention
The present invention relates to a method for producing an L-amino acid using a bacterium. L-Amino acids are industrially useful as additives for animal feeds, ingredients in seasonings, foods and drinks, amino acid infusions, and so forth.
2. Brief Description of the Related Art
L-Amino acids are industrially produced by, for example, fermentation using various microorganisms having an L-amino acid-producing ability. Examples of methods for producing an L-amino acid by fermentation include, for example, methods using a wild-type microorganism (wild-type strain), methods using an auxotrophic strain derived from a wild-type strain, methods using a metabolic regulation mutant strain derived as a mutant strain resistant to any of various drugs from a wild-type strain, and methods using a strain having characteristics as both an auxotrophic strain and metabolic regulation mutant strain.
Further, in recent years, microorganisms in which an L-amino acid-producing ability is improved by recombinant DNA techniques are used for the L-amino acid production. Examples of methods for improving an L-amino acid-producing ability of a microorganism include, for example, enhancing the expression of a gene coding for an L-amino acid biosynthetic enzyme (U.S. Pat. No. 5,168,056 and U.S. Pat. No. 5,776,736), and enhancing inflow of a carbon source into an L-amino acid biosynthesis system (U.S. Pat. No. 5,906,925).
The acpP gene is a gene coding for the acyl carrier protein (ACP) (Zhang Y, Cronan J E Jr., J Bacteriol., 1996 June; 178(12)3614-20). ACP is translated as inactive apo-ACP, then a cofactor 4′-phosphopantetheine is added to the serine residue at the position 36 (in the case of Escherichia coli) of apo-ACP by ACP synthase, and apo-ACP is thereby converted into active holo-ACP. The ACP protein plays an important role in the fatty acid biosyntheses of bacteria, and so forth. Specifically, in the fatty acid biosynthesis, ACP (holo-ACP) binds to a fatty acid chain via the 4′-phosphopantetheine group, thereby to carry the fatty acid chain
The fabF gene is a gene coding for β-ketoacyl-ACP synthase II (Zhang Y, Cronan J E Jr., J Bacteriol., 1996 Jun; 178(12)3614-20). The β-ketoacyl-ACP synthase II is one of the fatty acid biosynthesis enzymes, and participates in extension of fatty acid chain. Specifically, β-ketoacyl-ACP synthase II catalyzes the reaction that generates a 3-oxoacyl-ACP (carbon number=n+2) from an acyl ACP (carbon number=n) and malonyl-ACP (EC 2.3.1.41).
In Escherichia coli, the genes that participate in the biosynthesis of fatty acid, including the acpP gene and fabF gene, exist as the yceD-rpmF-plsX-fabHDG-acpP-fabF gene cluster. The genes of this gene cluster are co-transcribed as several gene pairs (Zhang Y, Cronan J E Jr., J Bacteriol., 1996 June; 178(12)3614-20). For example, the acpP gene and the fabF gene are co-transcribed as the acpP-fabF operon. In addition, the fabF gene is also independently transcribed with its own promoter. Furthermore, the acpP gene may also be co-transcribed from the fabD gene and the fabG gene in the yceD-rpmF-plsX-fabHDG-acpP-fabF gene cluster.
However, relationship between the acpP and fabF genes, and L-amino acid production has not been previously reported.